In recent years, the popularity of sport utility vehicles has risen tremendously. Because of the high ground clearance of these vehicles, the vehicle floor level is higher than that of a typical passenger automobile. Some individuals have experienced difficulty entering and exiting sport utility and similar high ground clearance vehicles.
Step structures have been used to assist passengers in entering and exiting high ground clearance vehicles. The conventional step structures have typically included a variety of stationary step or bar structures rigidly mounted to the vehicle. Stationary step structures have many disadvantages, however. For example, if a stationary step structure is positioned at an optimum height to help most passengers, the stationary step structure reduces ground clearance of the vehicle. If the stationary step structure is positioned so that desirable ground clearance is maintained, the stationary step structure is too high to help most passengers enter or leave the vehicle. Stationary step structures also detract from the vehicle styling, undesirably increase the vehicle width, and may even increase the vehicle width beyond the legal limit. Most stationary step structures are also very narrow in the transverse or cross-vehicle direction and present only a small stepping surface for a passenger's foot.
The patent literature has proposed various retractable vehicle step structures in order to resolve some of the problems associated with stationary step structures. For example, U.S. Pat. No. 3,762,742 proposes to provide a step that is pivoted about an axis that is angled in an outboard direction as it extends upwardly. While such angling of the pivotal axis enables the step structure to be positioned closer to the ground when deployed in comparison to its position when stored, the optimum step structure positioning in the two positions is not achieved. In addition, many of the proposed retractable step structures, such as that disclosed in the aforementioned '742 patent, do not provide the moving mechanical parts of the retractable step structure with effective protection from the environment or from damage caused by dirt and other objects thrown by the vehicle wheels when the vehicle is moving.
It is an object of the present invention to overcome the disadvantages of the proposed prior art devices as discussed above. Accordingly, the present invention provides a power-retractable step assembly for a motor vehicle comprising a substantially sealed housing assembly, a pivoting structure including a step structure, a gear assembly, and a motor assembly. The step structure presents an upper load carrying surface, and the pivoting structure is mounted for pivotal movement about an axis. The gear assembly is disposed in the sealed housing assembly and coupled to the pivoting structure. The motor assembly is drivingly coupled with the gear assembly and is constructed and arranged to pivot the pivoting structure about the axis and thereby drive the pivoting structure between deployed and stored positions. The step structure is moved in an outboard vehicle direction when the pivoting structure is moved from the stored position to the deployed position, and is also moved in a fore-aft vehicle direction when the pivoting structure is moved between the stored and deployed positions. The axis is disposed at an angle such that, as the axis extends upwardly, i) the axis extends in the outboard vehicle direction and ii) the axis extends in a same fore-aft vehicle direction as the fore-aft direction that the step structure moves when the pivoting structure is moved from the stored position to the deployed position.
Furthermore, several of the proposed mechanisms for powered retractable step structures, including the aforementioned '742 patent, do not provide a means for retracting the step from the deployed position in the event of a power failure, or for preventing damage to the step in the event that the deployed step forcibly encounters an object. It is a further object of the present invention to overcome this deficiency. Accordingly, the present invention provides a power-retractable step assembly for a motor vehicle comprising a pivoting structure including a step structure, a gear assembly, a motor assembly, and a spring-biased clutch assembly. The step structure presents an upper load carrying surface. The gear assembly is coupled to the pivoting structure, and the motor assembly is drivingly coupled with the gear assembly. The motor assembly is constructed and arranged to pivot the pivoting structure about the axis and thereby drive the pivoting structure between deployed and stored positions. The step structure moves in an outboard vehicle direction when the pivoting structure is moved from the stored position to the deployed position, and also moves in a fore-aft vehicle direction when the pivoting structure is moved between the stored and deployed positions. The gear assembly includes a worm gear operatively connected to the motor assembly and a meshing gear operatively connected to the pivoting structure. The worm gear and the meshing gear are disposed in cooperative meshing engagement relation that prevents the pivoting structure from backdriving the motor assembly so that the pivoting structure is retained in the deployed position and is inhibited from returning to the stored position after it has reached the deployed position. The spring biased clutch assembly couples the gear assembly with the pivoting structure and includes clutch surfaces normally forced into coupling engagement by a spring structure so that movement of the gear assembly generates corresponding movement of the pivoting structure. The clutch surfaces are capable of relative movement to one another when the pivoting structure is in the deployed position and a greater than threshold force is applied to the pivoting structure to overcome the force provided by the tension spring and thereby enable the pivoting structure to be moved relative to the gear assembly and thus moved towards the stored position.
These and other objects of the invention will become apparent from the following detailed description and appended claims.